Pressure regulators equipped with variable pressure regulator pilot valves are used as operating regulators, monitors, stand-by regulators and relief valves. Prior to the invention of U.S. Pat. No. 5,762,102, such valves were designed to maintain the desired pressure of fluid in a delivery line by operating with a constant “bleed” from the valve. This was not only wasteful but, in the case of some fluids, was environmentally undesirable. Environmental costs and problems are caused by discharge of pollutants to the air. Bleed gas from natural gas pipelines to the atmosphere year after year only adds to the growing environmental problem. Overall, industry estimates place the discharge of natural gas to the atmosphere from a single controller operating with constant bleed to the atmosphere, in excess of 300,000 standard cubic feet (SCF) per year.
In the present invention, while the no-bleed controller is of import, embodiments of the present invention address problems with the following key features:                VPC with one common block and external manifolds;        VPC with two different internal loading valves;        VPC with Manual Operation Valve (Rotary Type)—attached via manifold configuration;        VPC with external insertion of Nozzle Assembly;        VPC-PID with variable gain;        System configurations above adaptable to diaphragm style rotary pneumatic positioner via addition of proportional feedback mechanism;        Double-acting, single-acting (reverse) and single-acting (direct) in one common VPC configuration;        VPC with conditioning of output and exhaust flow paths via manifolds;        Interchangeability of “normally open” and “normally closed” internal loading valves in same body; and        Coupling of the “derivative” adjustable orifice on output of “ID” models—derivative adjustment is configured in manifold system and also incorporates “flow conditioning.”        
These and other problems are solved by the present VPC device and system.